A lot has been written on the last 2 and 3 strides to the board. This segment of the approach run is absolutely crucial for the jumper. This speed can not be wasted. There are certain technical and bio-mechanical elements that must be realized.
Firstly, the jumper, as he / she is placing the take-off foot / leg on to the board must PREPARE to make contact with the board. All musculature of the legs must be 'firmed' so that on contact the leg does not bend excessively behind the knee. Any knee bend will lower the center of mass so that the resulting parabola [flight path] will be very low resulting in a shorter distance being jumped.
Secondly, the arms positioning must be correct because the arms and shoulders help greatly in achieving a good vertical impulse.
So in the case of a left legged take-off the left arm will contribute approximately 25% to the lift.
Thirdly, as the take-off foot makes contact the 'other side' must attempt to drive up immediately. There should be no time lapse between contact and free leg drive whereby the jumper is attempting bring the free thigh to the parallel. Too often, novice jumpers and some more experienced jumpers do not bring this other side 'into play' fast enough.
There are many drills out there that can help in this development. I shall outline some of them in the second half of the article.
Young jumpers must understand that there is a definite correlation [mutual relationship] between touchdown, arms and free leg drive.
Part 2 will follow shortly and will explain more fully the action of the hip at take-off.